Display apparatus using electroluminescence elements

• US 6,084,579 A
• Filed: 11/25/1997
• Issued: 07/04/2000
• Est. Priority Date: 11/29/1996
• Status: Expired due to Term

• Current Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Hirano, Kiichi
• Primary Examiner(s): Powell, Mark R.
• Assistant Examiner(s): Blackman, Anthony J.
• Application Number:
  US08/978,262
• Time in Patent Office: 952 Days
• Field of Search: 345/76-81, 345/205, 313/498-512, 315/169.3
• US Class Current: 345/205
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/08 Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/089 Pixel comprising a non-linear two-terminal element in series with each display pixel element, the series comprising also other elements
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• CPC Class Codes: G09G 3/3216 using a passive matrix
• CPC Class Codes: G09G 3/3225 using an active matrix
• CPC Class Codes: H10K 59/1216 the pixel elements being capacitors
• CPC Class Codes: H10K 59/123 Connection of the pixel electrodes to the thin film transistors [TFT]

Abstract

A pixel of an organic electroluminescence (EL) display apparatus includes an EL element and an added capacitor connected in parallel with the EL element. The added capacitor provides improved image quality. To further improve image quality, an added resistor may be connected in series with the EL element, and in parallel with the added capacitor. Alternatively, the added resistor may be connected in series with the added capacitor, and in parallel with the EL element. The pixel may be used in both a simple matrix display system or an active matrix display system.

Claims

1. A display apparatus of a simple matrix system, comprising:

a matrix of pixels, each pixel including;

an electroluminescence element having a first electrode, a second electrode and a luminous element layer provided between said first electrode and said second electrode,

an insulator film provided over one of said first electrode and said second electrode, and

a third electrode provided in or over said insulator film so as to face one of said first electrode and said second electrode, said one of said first and second electrodes, said third electrode and said insulator film forming an added capacitor,

wherein said added capacitor is connected in parallel to said electroluminescence element, and wherein each pixel includes an added resistor for restricting a current flowing in said electroluminescence element from said added capacitor.

2. The display apparatus according to claim 1, wherein said luminous element layer comprises an organic compound.

3. The display apparatus according to claim 1, wherein said luminous element layer includes a luminous layer and at least one of a hole transporting layer and an electron transporting layer, which is located over the luminous layer.

4. An improved display apparatus comprising:

electroluminescence elements;

added capacitors connected in parallel to each of said electroluminescence elements, respectively, and

added resistors for restricting currents flowing in said electroluminescence elements from said added capacitors, respectively,

wherein each of said added resistors comprises a variable resistor which has a high resistance when said each added capacitor is discharged.

5. An improved display apparatus comprising:

electroluminescence elements;

added capacitors connected in parallel to each of said electroluminescence elements, respectively, and

added resistors for restricting currents flowing in said electroluminescence elements from said added capacitors, respectively, wherein each of said added resistors includes a P type impurity layer and an N type impurity layer connected to said P type impurity layer.

6. An improved display apparatus comprising:

electroluminescence elements;

added capacitors connected in parallel to each of said electroluminescence elements, respectively, and

added resistors for restricting currents flowing in said electroluminescence elements from said added capacitors, respectively, wherein each of said added resistors is connected in series with each of said electroluminescence elements and each of said added capacitor is connected in parallel to the series circuit of said each electroluminescence element and said each added resistor.

7. An improved display apparatus comprising:

electroluminescence elements;

added capacitors connected in parallel to each of said electroluminescence elements, respectively, and

added resistors for restricting currents flowing in said electroluminescence elements from said added capacitors, respectively, wherein each of said added resistors is connected in series with each of said electroluminescence elements and each of said added capacitor is connected in parallel to the series circuit of said each electroluminescence element and said each added resistor, and wherein each of said added resistors has a generally constant resistance.

8. An improved display apparatus comprising:

electroluminescence elements;

added capacitors connected in parallel to each of said electroluminescence elements, respectively, and

added resistors for restricting currents flowing in said electroluminescence elements from said added capacitors, respectively, wherein each of said resistors is connected in series with each of said electroluminescence elements and each of said added capacitor is connected in parallel to the series circuit of said each electroluminescence element and said each added resistor, and wherein each of said added resistors comprises a variable resistor which has a high resistance when said each added capacitor is discharged.

9. An improved display apparatus comprising:

electroluminescence elements;

added capacitors connected in parallel to each of said electroluminescence elements, respectively, and

added resistors for restricting currents flowing in said electroluminescence elements from said added capacitors, respectively, wherein each of said added resistors is connected in series with each of said electroluminescence elements and each of said added capacitor is connected in parallel to the series circuit of said each electroluminescence element and said each added resistor, and wherein each of said added resistors includes a P type impurity layer and an N type impurity layer connected to said P type impurity layer.

10. An improved display apparatus comprising:

electroluminescence elements;

added capacitors connected in parallel to each of said electroluminescence elements, respectively, and

added resistors for restricting currents flowing in said electroluminescence elements from said added capacitors, respectively, wherein each of said added resistors is connected in series with each of said added capacitors, and each of said electroluminescence elements is connected in parallel to the series circuit of said each added capacitor and said each added resistor.

11. An improved display apparatus comprising:

electroluminescence elements;

added capacitors connected in parallel to each of said electroluminescence elements, respectively, and

added resistors for restricting currents flowing in said electroluminescence elements from said added capacitors, respectively, wherein each of said added resistors is connected in series with each of said added capacitors, and each of said electroluminescence elements is connected in parallel to the series circuit of said each added capacitor and said each added resistor, and wherein each of said added resistors has a generally constant resistance.

12. An improved display apparatus comprising:

electroluminescence elements;

added capacitors connected in parallel to each of said electroluminescence elements, respectively, and

added resistors for restricting currents flowing, in said electroluminescence elements from said added capacitors, respectively, wherein each of said added resistors is connected in series with each of said added capacitors, and each of said electroluminescence elements is connected in parallel to the series circuit of said each added capacitor and said each added resistor, and wherein each of said added resistors comprises a variable resistor which has a high resistance when said each added capacitor is discharged.

13. An improved display apparatus comprising:

electroluminescence elements;

added capacitors connected in parallel to each of said electroluminescence elements, respectively, and

added resistors for restricting currents flowing in said electroluminescence elements from said added capacitors, respectively, wherein each of said added resistors is connected in series with each of said added capacitors, and each of said electroluminescence elements is connected in parallel to the series circuit of said each added capacitor and said each added resistor, and wherein each of said added resistors includes a P type impurity layer and an N type impurity layer connected to said P type impurity layer.

14. A display apparatus of an active matrix system, the apparatus comprising:

a matrix of pixels; and

driving elements, for driving the matrix of pixels, respectively, wherein the each pixel includes;

an electroluminescence element having a first electrode, a second electrode and a luminous element layer provided between said first electrode and said second electrode,

an insulator film provided over one of said first electrode and said second electrode, and

a third electrode provided in or over said insulator film so as to face one of said first electrode and said second electrode, one of said first and second electrodes, said third electrode and said insulator film forming an added capacitor, wherein said added capacitor is connected in parallel to said electroluminescence element, and wherein each pixel includes an added resistor for restricting a current flowing in said electroluminescence element from said added capacitor.

15. The display apparatus according to claim 14, wherein said driving element comprises a thin film transistor.

16. The display apparatus according to claim 14, wherein said luminous element layer comprises an organic compound.

17. The display apparatus according to claim 14, wherein said luminous element layer includes a luminous layer and at least one of a hole transporting layer and an electron transporting layer, which is located over the luminous layer.

18. The display apparatus according to claim 14, wherein said added resistor has a generally constant resistance.

19. The display apparatus according to claim 14, wherein said added resistor comprises a variable resistor which has a high resistance when said added capacitor is discharged.

20. The display apparatus according to claim 14, wherein said added resistor includes a P type impurity layer and an N type impurity layer connected to said P type impurity layer.

21. The display apparatus according to claim 14, wherein said added resistor is connected in series to said electroluminescence element and said added capacitor is connected in parallel to the series circuit of said electroluminescence element and said added resistor.

22. The display apparatus according to claim 21, wherein said added resistor has a generally constant resistance.

23. The display apparatus according to claim 21, wherein said added resistor comprises a variable resistor which has a high resistance when said added capacitor is discharged.

24. The display apparatus according to claim 21, wherein said added resistor includes a P type impurity layer and an N type impurity layer connected to said P type impurity layer.

25. The display apparatus according to claim 14, wherein said added resistor is connected in series to said added capacitor, and said electroluminescence element is connected in parallel to the series circuit of said added capacitor and said added resistor.

26. The display apparatus according to claim 25, wherein said added resistor has a generally constant resistance.

27. The display apparatus according to claim 25, wherein said added resistor comprises a variable resistor which has a high resistance when said added capacitor is discharged.

28. The display apparatus according to claim 25, wherein said added resistor includes a P type impurity layer and an N type impurity layer connected to said P type impurity layer.

29. A pixel for use in a matrix of pixels of a display apparatus, the pixel comprising:

an electroluminescence (EL) element having a first electrode, a second electrode and a luminous element layer disposed between the first and second electrodes;

an insulator disposed over the first electrode;

a third electrode provided in or over the insulator so as to face the first electrode, wherein the first electrodes, said third electrode and said insulator film form an added capacitor, and

an added resistor disposed over the second electrode for restricting a current flowing in said electroluminescence element from said added capacitor.

30. A pixel of an organic EL display apparatus, the pixel comprising:

an organic EL element;

an added capacitor connected in parallel to the EL element, and

an added resistor connected in series with the EL element, such that the EL element and the added resistor are connected in parallel with the added capacitor.

31. The pixel of claim 30, wherein the organic EL element comprises:

an anode;

a hole transporting layer disposed on a surface of an anode;

a luminous layer disposed on a surface the hole transporting layer;

an electron transporting layer disposed on a surface of the luminous layer; and

a cathode disposed on the electron transporting layer.